1. Field of the Invention
The invention relates generally to bicycle handlebars.
2. Description of Prior Art and Related Information
FIG. 1 shows a conventional handle structure in a typical bicycle. As illustrated in FIG. 1, in the typical handle structure two fork legs 108, on the left and the right, having a mechanism for steering while supporting the axle of a front wheel 114, are connected by a fork crown 113 above the front wheel 114. Given this, the upper portion of the fork crown 113 is connected to a single steering column, or steering tube, 111. Additionally, the top end of the steering column 111 is connected to the handlebar 100, at a center portion 102, through a connecting component of a stem 109.
Moreover, the steering column 111 is borne rotatably in a front frame 17 through a head tube 10 of a front frame 17 (structured from a head tube 10, a top tube 15, and a down tube 16). Moreover, the axle of the front wheel is supported by dropouts (not shown) positioned at the bottom ends of the fork legs 108.
In this way, usually the typical bicycle handlebar is secured by a single stem at one location in the center portion thereof (for example, see Japanese Unexamined Patent Application Publication H7-300088). Because of this, the center portion of the handlebar, which serves as the position for attaching the stem, is subjected to strong loads through operation of the handle during riding. Moreover, along with the load due to operation of the handle, there are stresses because the handlebar is secured by the stem, and stresses due to the stem attaching position acting as a lever fulcrum. At these points, the center portion, which is the position in the conventional handlebar for attaching the stem, must have strength and rigidity greater than that of other portions.
That is, because in existing handlebars the design assumes that the handlebar will be secured using a stem in a single location in the center portion, it is necessary to increase the strength of the handlebar overall. Therefore, the diameter of the conventional handlebar is necessarily large, and the thickness of the material also large, making the prior art handlebar heavy.
FIG. 2 illustrates a handlebar that is attached to a stem in a single location in the center portion. As illustrated in FIG. 2, the handlebar 201 is a handlebar having a height difference between a center portion 202 and grip portions 4a and 4b, where a stem attaching position 203 is provided in a single location in the center portion 202. Because of this, if the strength of the center portion 202, which is at the stem attaching position 203, were reduced, then it would not be possible to maintain the strength of the handlebar. Consequently, in a handlebar of a shape wherein the stem is attached to a single location at the center portion, the structure of the present invention cannot be used.